The effect of different levels of additional potassium on yield and industrial qualities of potato (Solanum tuberosum L.) in an irrigated arid region

Soils and irrigation waters in Saudi Arabia are naturally rich in potassium (K). In spite of this, farmers and large-scale agricultural companies usually add K fertilizers to various crops without soil and water testing and whether or not the crop requires high amount of K. The objective of these experiments was to study the response of fresh tuber yield, specific gravity, and frying quality of processed potato to different levels of additional K under farmer conditions. Two field experiments were conducted during the 2000-2001 and 2001-2002 growing seasons in Wadi Addawasir (latitude 20-21 N, longitude 45-46 E), Kingdom of Saudi Arabia. The experimental layout was a randomized complete block design with five K levels (0-100 kg K2O ha(-1)) and four replicates. Water and soils in this region contained more than 10 and 200 ppm K, respectively. Results indicated that there were no statistical differences (P<0.05) between the levels of K on fresh tuber yield, specific gravity, or frying quality. Similarly, K content of leaves at 45 or 60 days after emergence and of tubers at harvest was not significantly affected (P<0.05) by K rates. Potassium content in leaves was above optimum level. Results of this study indicated that current application rates of K are higher than the potato crop requirement for optimum yield obtained in this region. Results also indicated that farmers' basic application of 215 kg K2O ha(-1) along with soil native K and irrigation water K were sufficient to produce economic yield and high-quality potatoes.